The effect of a supersonic plasma jet expansion on a magnetized, ambient plasma measured using laser-induced fluorescence

The supersonic expansion of a laser-produced carbon plasma through an ambient argon plasma ($n\sim2\cdot10^{12}cm^{-3},c_{s}=4\cdot10^{5}cm/s$) is studied in the Large Plasma Device at UCLA. A laser-induced fluorescence diagnostic characterized the interface of the plasma species' populations as the carbon plasma expands ($\tau_{exp}\sim.5\mu s$) along the background magnetic field. A planar beam of a YAG-pumped, tunable dye laser sampled the distribution function of the Ar-II ions using the Doppler broadened transition at 611.5 nm. A CCD camera with a fast ($\geq$3 ns) shutter provided a spatially and temporally resolved image of the fluorescence. Time lapsed imaging revealed a front of argon ion excitation moving at a speed comparable to the carbon parallel expansion velocity ($v_{exp}\sim1\cdot10^{7}cm/s$) while the distribution function from the transition spectra showed a significant fraction of argon ions accelerated to an ion sound speed mach number of 2-3. The laser-induced fluorescence measurements are supplemented by magnetic and Langmuir probe measurements.